[15] Wrong stock quantity by location on product.template

[jprokop1]

After migration to 15.0 the stock quantity on locations from product views (model product.template) are wrong, but from variants view (model product.product) OK.
Quick and dirty fix in stock_location.py (only for one variant by product):
if template_id:
product = self.env['product.product'].search([("product_tmpl_id", "=",template_id)] )[0]

Regards

Jan